1. Field of the Invention
This invention pertains to blowout prevention systems for subsea wellheads, and more particularly to blowout prevention systems that serve as a backup or fail safe system to existing primary blowout prevention systems.
2. Description of the Related Art
For subsea drilling operations, if the pressure of the formation fluids exceeds the hydrostatic of the fluid in the well bore and the associated surface pressure applied, a blowout emergency may develop. Heretofore, the blowout emergency is managed by the operational personnel on the offshore drilling unit using a subsea blowout prevention system (hereinafter referred to as ‘BOP system’) that is attached to the wellhead on the seafloor.
Federal regulations require that all offshore drilling operations use a ‘BOP system’ that include different types of ram assemblies, annular seals, remote operated valves, a marine riser, diverter, tensioners, and a redundant control system managed from the drilling unit located on the surface of the water.
A typical ‘BOP system’ connects to the top of the wellhead housing using a cylindrical wellhead connector. The wellhead housing is found near the seabed and remains in place after the drilling unit has completed its operation and has been removed. The wellhead housing is designed to withstand all the stresses generated by the ‘BOP system’ and the marine riser running back to the drilling rig.